The overall objective of the present research program is to delineate the mechanisms other than changes in plasma osmolality which are involved in the regulation of renal water excretion. The investigations will be performed in experimental animals and human subjects. Experiments will be undertaken to examine the afferent and efferent mechanisms whereby alpha and beta adrenergic stimulation and prostaglandins influence the renal excretion of water. The pathways whereby adrenocortical hormones and maneuvers which influence systemic hemodynamics and tubular sodium reabsorption alter renal water excretion will also be investigated. The experimental design of all these studies will be as such as to allow the evaluation and integration of alterations in systemic, cerebral and renal hemodynamics, activity of the renin-angiotensin system, renal cyclic AMP and autonomic neural tone in the mechanisms of non-osmolar regulation of renal water excretion.